Abstract
Cardiac function has been shown to transiently decrease following prolonged exercise, with greater durations related to increased impairment. However, the prospective assessment of exercise duration on cardiac performance is rare, and the influence of relative exercise intensity is typically not assessed in relation to these changes. The aim of this study was to determine whether progressively longer running distances over the same course would elicit greater cardiac impairment. The present investigation examined cardiac alterations in 49 athletes, following trail-running races of 25, 50, 80, and 160 km, performed on the same course on the same day. Echocardiography, including conventional and speckle tracking imaging, was performed with legs-raised to 60° to mitigate alterations in preload both pre- and post-race. Race-intensities were monitored via heart rate (HR). Following the races, mean arterial pressure (Δ−11 ± 7 mmHg, P < 0.0001), and HR (Δ19 ± 14 bpm, P < 0.0001) were altered independent of race distance. Both left and right ventricular (LV and RV) diastolic function were reduced (ΔLV E/A −0.54 ± 0.49, P < 0.0001; ΔRV A’ + 0.02 ± 0.04 m/s, P = 0.01) and RV systolic function decreased (ΔTAPSE −0.25 ± 0.9 cm, P = 0.01), independent of race distance. Cardiac impairment was not apparent using speckle tracking analysis with cubic spline interpolation. While race duration was unrelated to cardiac alterations, increased racing HR was related to greater RV base dilation (r = −0.37, P = 0.03). Increased time spent at higher exercise intensities was related to reduced LV ejection fraction following 25 km (r = −0.81, P = 0.03), LV systolic strain rate following 50 km (r = 0.59, P = 0.04), and TAPSE (r = −0.81, P = 0.03) following 80 km races. Increased running duration did not affect the extent of exercise-induced cardiac fatigue, however, intensity may be a greater driver of cardiac alterations.
Highlights
Mass participation in prolonged endurance exercise events has increased greatly over the past few decades (Hoffman, 2016)
One study to date has directly examined whether greater distance races of a given type of exercise results in greater cardiac fatigue, and it was found that both half (70.3 mile) and full (140.6 mile) longdistance triathlons induced similar diastolic cardiac alterations, with greater reductions to left ventricular (LV) ejection fraction and fractional shortening following the longer event (Whyte et al, 2000)
In a previous meta-analysis it was shown that LV systolic function may require over 10 h of prolonged exercise before alterations become apparent in trained individuals (Middleton et al, 2006), it was demonstrated that 1 h of criterium cycle racing, performed at near-maximal intensity (∼88% of maximal heart rate) by well-trained cyclists, was sufficient to elicit alterations in systolic function under controlled-loading conditions (Stewart et al, 2015)
Summary
Mass participation in prolonged endurance exercise events has increased greatly over the past few decades (Hoffman, 2016). There is evidence that prolonged strenuous exercise may transiently alter both left ventricular (LV) (Middleton et al, 2006; Lord et al, 2018) and right ventricular (RV) (Oxborough et al, 2011; Elliott and La Gerche, 2014) function This alteration is often termed “exercise induced cardiac fatigue,” and event duration and participant cardiorespiratory fitness are thought to play a role in the severity of the associated change (Middleton et al, 2006; La Gerche et al, 2012). This has implications for future research, and whether or not there are clinical consequences of exercise induced cardiac fatigue
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